The latest research into the dangers of trans fats in relation to obesity tells us that not all calories are equal. And certainly not all fats are equal.

In May 2006, researchers at Wake Forest University reported, after a six-year study, that calories from trans fats made laboratory monkeys fatter than calories from other forms of fat. And this was in spite of efforts by the researchers to prevent the monkeys from gaining weight, by placing them on a low calorie diet.

The researchers also found that calories from trans fats made the monkeys much fatter around the tummy.

Trans fats re-distributed body fat, moving fat from other parts of the body to the abdomen area, thereby creating the “pear-shape” figure that has been strongly associated with heart disease, diabetes and other illnesses.

Lawrence Rudel, Ph.D., who headed the research, declare that the dangers of trans fats are worse than anticipated.

Other scientists are now saying that we need to re-think the whole idea that weight gain depends on calorie intake – because the latest study shows that even low calorie diets can produce weight gain if those calories come from trans fats.

In the Wake Forest study, researchers were originally investigating the dangers of trans fats in causing arteriosclerosis, or plaque build-up in the arteries.

In the study, researchers fed 51 male vervet monkeys a western-style diet, which had 35 percent of their diet coming from fats. Half the monkeys got a lot of trans fat, totaling 8 percent of their total calorie intake. The other monkeys were fed unsaturated fats such as olive oil.

Both types of diets were calorie-controlled, as the researchers did not want the monkeys to put on weight. This was to ensure that whatever dangers of trans fats found during the research were due to trans fat intake, and not to other factors such as weight gain.

So in theory, the monkeys should not have gained weight. But they did.

Over six years -- equivalent to a 20-year span for humans -- the monkeys who ate unsaturated fats increased their body weight only marginally, by 1.8 percent. Monkeys that were given trans fats, howver, put on 7.2 percent more weight.

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Dangers of trans fats – diabetes

A 7.2 percent weight gain may not seem much. But it is significant for two reasons:

• The monkeys were not supposed to gain any weight at all
  
  
• Even a 5 percent weight gain is enough to increase a person's risk of diseases like diabetes.

Said Dr Kylie Kavanagh, who reported the findings at the annual meeting of the American Diabetes Association in Washington:

"In the world of diabetes, everybody knows that just 5 percent weight gain or weight loss makes an enormous difference. This little difference was biologically quite significant."

The trans-fat eating primates also had higher blood glucose levels and were more insulin resistant than their counterparts. In other words, the monkeys were showing early signs of Type II diabetes or adult-onset diabetes.